| dc.description.abstract |
Premature failures, including the development of early cracks, potholes are the
major causes of the high annual road maintenance cost of Bangladesh.
Modification of traditional bitumen by different types of polymers could be an
effective solution to reduce this huge maintenance cost of pavement. To
incorporate this modification in the conventional flexible pavement of our
country, this study investigated the effect of Pyrolysis Carbon Black (PCB) and
Polypropylene (PP) on both bitumen and bituminous mix. Pyrolysis Carbon
Black (PCB), an elastomer and one of the by-products of the scrap tire pyrolysis
process, had been recognized as one of the most efficient modifiers in several
studies. Being a waste product, modification of asphalt with PCB could
contribute to waste management problems as well. 2%, 3%, 5%, 10% and 15%
PCB of total bitumen content was used for modification. Another modifier used
for modification was polypropylene (PP). For polypropylene, the percentages
used were 1 %, 2%, and 3%. Based on the results of two individual polymers,
two combinations consisting of both PP and PCB were prepared as well. To
ensure a homogeneous blending, all the modified bitumen was prepared
through the wet process by using a mechanical blending device. Penetration,
softening point, ductility, specific gravity tests were performed on unmodified
and modified bitumen for evaluating the physical properties. The penetration
and ductility values showed a decreasing trend with increased polymer content
for all types of modified bitumen. But an increasing trend had been observed in
the case of a softening point. The mechanical properties of the bituminous mix
ii
were investigated through Marshall, Indirect Tensile Strength (ITS) test. To
investigate the resistance to moisture damage, the retained Marshall stability
test was performed on some specific bituminous mix. The stability of the
bituminous mix with 3% PCB was approximately 51% greater than that of the
unmodified mix. In the case of PP modified bitumen, a 22 % increase was found
in stability value for the incorporation of 3 % PP in neat bitumen. The stability
of the two combinations of PCB and PP increased by 29% from that of the
unmodified bituminous mix. Significant improvement was observed in retained
Marshall stability and ITS value for polymer modification. The retained
stability increased from 74% to 90% for a combination of 3% PCB and 2%PP.
The highest ITS and retained Marshall stability was observed for combined
modified bitumen consisting of 3% PCB and 2%PP. From this study, it was
confirmed that modification of bituminous mixes with PCB and PP could
decrease the premature failure problem of Hot Mix Asphalt (HMA) pavement
to some extent by increasing resistance to moisture damage, high-temperature
susceptibility, load-bearing capacity. The findings of this study would motivate
the road agencies of the country to use the modified bitumen instead of
conventional bitumen to enhance the performance of the flexible pavement. |
en_US |
